The invention relates to an optical pickup head. More particularly, the invention provides a pickup head that can be manufactured via semiconductor planar fabrication processes so that the size of the pickup head can be reduced while it can be used to read and write on high-density disks.
The function of an optical head is to focus a laser beam emitted from a laser source into a focus spot on a data layer of the disk and further precisely maintain this focus spot to perform reading, writing, and erasing operations on the disk.
Referring to FIG. 1, a schematic view illustrates an operation of a conventional optical pickup head. When a reading operation is performed, a laser beam emitted from a laser source 1 diverges along the light path 2A onto a beam splitter 3. A portion of the laser beam then is reflected toward a collimator 4 to become parallel. Via a folding mirror 5, the horizontal laser beam then is upwardly reflected toward an objective lens 6 to be focused and projected onto a disk 7. After reflection from the disk 7, the laser beam passes through the objective lens 6, the folding mirror 5, and the collimator 4 to the beam splitter 3. A portion of the laser beam passes through the beam splitter and travels along the light path 2B toward a photo-detector 8. The photo-detector 8 then converts the light signal into an electrical signal that includes data signal from the disk, focus error signal, and track course error signal. The focus error signal and the track course error signal are processed via a server circuit. Subsequently, a resulting feedback current is delivered to a controller coil 9 of the objective lens 6 and a track course controller coil 10 to correct the focus error and the track course error. Thereby, a reading operation of the disk is correctly performed without error signals.
When a writing operation is performed, a function generator adjusts a driving current of the laser source 1 to obtain a desired variation of intensity of the laser beam. Resulting thermal actions of the laser beam, travelling through the above light path to be projected onto the disk, then create different physical features of the data layer of the disk corresponding to the data information written. An erasing operation is similar to the above writing operation except that the intensity of the laser beam is appropriately adjusted to create similar physical features on the data layer of the disk to achieve an erasure.
FIG. 2 is a perspective view that illustrates a conventional optical pickup head that operates according to the above mechanism. In the conventional optical pickup head, the beam splitter 3, the collimator 4, the folding mirror 5, and the objective lens 6 are mechanically constructed via a precise casting process, and are subsequently attached onto an element support base 11. Usually, the element support base 11 also requires a precise casting process to be fabricated. The laser source 1 and the photo-detector 8 are further attached onto side faces of the element support base 11.
Because the above elements are solid and spatially distributed on the element support base 11, the size of the optical pickup head therefore is not easily reduced. Furthermore, in the assembly stage, the mount of the above optical elements necessitates a precise positioning. As a result, the fabrication of the conventional optical pickup head is complicated to achieve and provides a low yield.
It is therefore a principal object of the invention to provide a planar integral micro-optical pickup head that can overcome the above difficulties of mechanical precise processes, precise positioning and assembly.
It is another object of the invention to provide a planar integral micro-optical pickup head that can be fabricated via semiconductor planar fabrication processes and simple alignment and attachment operations so that the size of the optical pickup head can be miniaturized.
Yet, it is another object of the invention to provide an optical pickup head that can read and write on high-density disks.